OTP Bypass Attacks

OTP bypass attacks defeat one-time-password authentication without ever knowing the user's password. The principal vectors are SIM swap (porting the victim's MSISDN to an attacker SIM), SS7 SMS interception, malware on the device that reads incoming OTPs, and adversary-in-the-middle phishing kits that relay the OTP in real time. Because all of these break SMS-based MFA, security guidance increasingly recommends FIDO2/WebAuthn or app-based push approval for high-value accounts.

Categories: Core NetworkSignalingIdentity and Subscriber

OTP Bypass Attacks in context

The mobile core is where subscriber sessions, mobility and policy live. In 4G it is the EPC (MME, HSS, S/PGW); in 5G it is the Service-Based Architecture with AMF, SMF, UPF, AUSF, UDM and the NRF. Core exposure is the difference between a single-subscriber leak and a fleet-wide breach.

Signaling protocols carry the control-plane instructions that set up calls, register subscribers, hand over sessions and route SMS. SS7, Diameter, GTP-C and SIP are the four dominant families, and interconnect exposure of any of them is treated by GSMA FS.11 / FS.19 / FS.20 as a top-tier telecom risk.

To place OTP Bypass Attacks in the wider telecom-security picture, review SMS, AMF, IAMF, MSC, SMSC and VoLTE.

Related terms

Related topic hubs

  • Signaling Firewall Unified SS7/Diameter/GTP/SMS signaling firewall framework.
  • SMS Firewall SMS spam, phishing, A2P bypass and MAP-layer SMS filtering.
  • SIM Swap Attack SIM swap fraud, port-out and account takeover risk.
  • SS7 Security SS7/MAP/CAP/SCCP attacks and defenses across 2G/3G interconnect.

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